The present invention relates to a method of producing an underground installation of concrete pipe and to a device useful in such method.
A number of methods are known for producing underground installations of concrete pipe, such as used in underground sewage systems. On method, called the "open trench" technique, involves digging open trenches, placing therein precast concrete pipe sections which are connected together, and then filling the trench. However, there are many conditions where this techinque is not possible or not practical. In such cases, a "pipe-pushing" technique, or a "pipe-pulling" technique, may be used. In the pipe-pushing technique, shafts are sunk into the ground at two spaced locations between which the concrete pipe is to be installed, and the concrete is pushed, by means of jacks, from one shaft towards the next shaft, consecutive sections of the pipe being attached after each pushing step. In the pipe-pulling technique, two shafts are also sunk into the ground. A steel pipe of larger diameter than the concrete pipe to be laid is then pulled from one shaft to the other by means of pulling cables extending from the pipe to the other shaft, the pulling being effected in steps, with a pipe section being welded to the trailing end after each pulling step. The soil is removed from the center of the steel pipe, and a concrete pipe is then laid within it, the outer steel pipe thereby serving as a liner. In another pipe-pulling techinque, a shield is disposed in one shaft and is pulled towards the other shaft by means of the pulling cables. As the shield is pulled through the ground, steel plates are attached after each pulling step to form a tunnel liner section extending the distance of the pulling step; and after the complete span has been thus lined, a pipe, for example of steel or concrete, is installed within the liner.